As others have noted…it’s all doable. However, if you come in on a 30 day visa exempt entry, get to the immigration office right away as there is an under consideration period. You want that under consideration period to end before your 30 days are up. Depending on the office, it may be three weeks so…hop right on it!
Have you considered converting to an “O” visa from the “O-A”? Sure, you need funds on deposit but if you plan to spend a long time in Thailand it may be better for you than paying for “less than good” insurance. Just a thought!
If you happen to be in Thailand after the last “enter by” date shown on your Non Imm O-A visa you can leave without a reentry permit and re-enter visa exempt (provided your from a country that is approved for visa exempt entry) and apply for the Non O. You don’t have to wait until the end of your permission to stay date. Just check to be sure you are past the last “enter by” date shown on your O-A. You can apply for the Non O from within Thailand.
TM30 is probably what you’re referring to. Each district has its own rules about updating the tm30 after arriving back in the country. Others will be along shore with updates…I’m sure!